Re: Saito Sensei's weapons
Kobayashi's weapons are Saito's weapons. Kobayashi's student K. Igarashi (now head of his own organization) helped M. Saito when he wrote the first books. Since then the aikiken and aikijo (with minor differences) were included as curricula at Kobayashi dojo.
Chiba sensei used M. Saito's weapon as a template (he was also in Iwama for a period of time) and has since developed his own set from these together with his training in iaido.
Homma sensei's weapons are essentially Saito senseis weapon. He was an uchi deshi in Iwama in the end of the 60's.
Saotome sensei's weapon I would say is the most unique and if I understood relatively self created.